Various polymers, swellable clays, and multi-layer articles of manufacture have been applied to the surface of soil to provide a waterproofing layer to prevent the penetration of water and/or hazardous or toxic materials into the earth, and to provide lagoons, ponds and other water-containment areas. Water-swellable clays, such as bentonite, have been applied directly to the soil surface and impacted in place, as disclosed in this assignee's prior U.S. Pat. No. 3,986,365. In addition, many different multi-layered articles of manufacture containing a water-swellable clay, such as sodium bentonite, have been manufactured by securing the water-swellable clay to major interior surfaces of flexible sheet materials, e.g., Clem U.S. Pat. No. 4,501,788, for application to the soil surface in abutting or overlapping relation to adjoining multi-layered articles. Examples of other flexible sheet materials containing adhesively secured water-swellable clays are found in the following Clem U.S. Pat. No. 4,467,015; McGroarty, et al. U.S. Pat. No. 4,693,923; Harriett U.S. Pat. No. 4,656,062; and Harriett U.S. Pat. No. 4,787,780.
U.K. published Patent Application GB 2,202,185A discloses a layer of water-swellable bentonite between flexible fabric layers that have been needle punched together in a needle loom that secures the upper and lower layers together, wherein at least one of the fabric layers is a non-woven textile material.
Another waterproofing barrier, disclosed in Blais U.S. Pat. No. 4,344,722, is constructed in the field by applying a first flexible, water-permeable fabric layer, overlaying a thickness of water-swellable clay material and applying an overlay of the same flexible, water-permeable fabric thereover. Other patents disclosing the use of water barrier layers for protecting a soil surface include British Patent Specification 1,059,363; British Patent Specification 1,029,513 and British Patent Specification 1,129,840.
German Patent DE 37 04 503 C2 discloses an article having two fabric layers including one non-woven fabric, surrounding a bentonite clay layer wherein the two fabric layers are needle punched together. Crawford U.S. Pat. No. 4,565,468 discloses an article including two fabric layers surrounding a bentonite clay layer wherein the two fabric layers are quilted together in a pattern forming four sided compartments. This assignee's U.S. Pat. No. 5,389,166, hereby incorporated by reference, describes incorporating a water swellable clay into a mat while laying down fiber to form the mat.
While the articles described in the above-mentioned patents are effective for waterproofing against the penetration of relatively non-contaminated water, they are unable to prevent the penetration of salt (e.g., NaCl) containing water, such as ocean water.
This assignee's application Ser. No. 11/942,638, filed Nov. 19, 2007, hereby incorporated by reference, discloses salt water-swellable acrylate copolymers that swell in contact with salt-contaminated water. As disclosed in this application, the copolymer is disposed against a membrane layer and serves to plug the membrane layer should the membrane develop a leak.
This assignee's research subsequent to filing Ser. No. 11/942,638 was directed to salt water-swellable compositions that would swell when in contact with salt-contaminated water, but would not require a contacting fabric or film layer, e.g., for plugging a space surrounding a pipe in a salt-water-contaminated area. This research revealed that the salt water-swellable acrylic copolymers disclosed in Ser. No. 11/942,638 would not remain sufficiently intact without an adherent fabric or film layer, e.g., for uses in rope or paste consistency form, such as disclosed in this assignee's U.S. Pat. Nos. 4,656,062; 4,810,573; 4,773,989; 4,787,780; 4,668,724; 4,534,926; and 5,580,630, each hereby incorporated by reference. Surprisingly, however, it was found that the composition could swell in contact with salt-contaminated water and stay cohesive so long as the composition includes (i) a cationic flocculant, together with (ii) partially netralized, partially cross-linked, water-insoluble acrylic acid/polyacrylamide copolymer, (iii) clay, (iv) an elastomer, such as butyl rubber and (v) a plasticizing agent such as polybutene, polypropene, polybutadiene, polyisobutene and/or polyisopropene. It should be understood that the compositions described herein can include one or more layers of woven or non-woven geotextile, and/or can include a layer of a water-soluble film, as disclosed and claimed in this assignee's U.S. Pat. No. 5,580,630, hereby incorporated by reference.
Surprisingly it has been found that compositions comprising (i) a partially cross-linked copolymer of acrylamide and partially neutralized polyacrylic acid, preferably a acrylamide/potassium acrylate, sodium acrylate/acrylic acid copolymer (CAS #312-12-13-2), e.g., STOCKOSORB, or STOCKOSORB S, or STOCKOSORB F from Stockhausen, Inc. of Greensboro, N.C.; together with (ii) a smectite clay; (iii) an elastomer, e.g., butyl rubber; (iv) a plasticizing agent such as polybutene, polypropene, polybutadiene, polyisobutene and/or polyisopropene; and (v) a cationic flocculant, will waterproof surfaces against the penetration of high conductivity water while remaining cohesive. The compositions and articles described herein are most useful to provide a water barrier against multivalent ion-containing water (“salt water”) having a conductivity of at least 15 mS/cm, preferably at least 20 mS/cm, more preferably at least 30 mS/cm, even more preferably at least 40 mS/cm, and most preferably at least 50 mS/cm.
Super absorbent polymers (“SAPs”) have been produced since the 1970s for use in a variety of products including, among others, hygiene products, such as disposable diapers, training pants, feminine hygiene products and incontinence devices, agricultural and horticultural products and industrial and environmental absorbents. SAPs are primarily utilized to increase or enhance the product's water-absorbency.
SAPs are produced from a variety of components by a variety of processes. For example, SAPs are often made from monomers such as acrylamide, acrylic acid and acrylate, which are particularly suitable for application in hygiene products.
Alternately, swelling clays, such as sodium smectite clays, e.g., sodium bentonite may be used to provide water-absorbency to a product. With respect to cost, the cost of swelling clays tends to be minimal compared to that of the chemical monomers described above. In addition, swelling clays are relatively stable compared to chemical monomers and are not as subject to degradation. However, swelling clays have a water absorption capacity significantly less than that of SAP, and like the common partially cross-linked partially neutralized acrylic acid copolymer SAPs, sodium smectites do not have sufficient free-swell when contacted by high conductivity salt water to act as a salt water barrier.
Some products include both an SAP and a swelling clay, as described in U.S. Pat. No. 6,610,780 and this assignee's U.S. Pat. No. 6,783,802, hereby incorporated by reference. Neither the SAPs nor the water-swellable clays, however, have been capable of waterproofing surfaces against the penetration of salt water, e.g., high conductivity, ion-contaminated water, such as ocean water.
It is well known that the montmorillonite group of clays hydrate and swell in fresh water but the swelling is substantially inhibited in salt water. Salt water is often encountered in the environments of use of bentonite clays where bentonite is advantageously employed for its swelling capacity, for example, as an additive in drilling muds for the purpose of sealing fissures in earthen formations surrounding the drill hole to prevent loss of drilling fluid; and in the sealing of lagoons and landfills. When contacted with salt water, the swelling capacity and stability of common montmorillonite clays are severely inhibited making it necessary to use much greater quantities of the clay to achieve the degree of swelling needed for sealing purposes. In some cases the palygorskite clays are used instead of the montmorillonite clays because of their better dispersing properties in salt water, as disclosed in U.S. Pat. No. 4,202,413.
In the past, modified bentonite clays have been developed by this assignee having a swelling capacity substantially less inhibited in salt water. Examples of such modified bentonites are the polymer treated bentonites disclosed in the Clem, U.S. Pat. Nos. 3,949,560; 4,021,402; 4,048,373 and 4,103,499.
The assignee's U.S. Pat. No. 4,634,538 teaches that one or more gums, such as xanthan gum, can be added to a water-swellable clay to improve its free swell when hydrated with salt water. This assignee's U.S. Pat. No. 5,578,219 describes impregnating a dried, water-swellable clay with an aqueous solution of a water-soluble polymer followed by re-drying to improve the ability of the clay to absorb contaminated water.
Partially cross-linked acrylamide/sodium or potassium acrylate/acrylic acid copolymers have been used for retention of water and plant nutrients in agriculture by mixing the copolymers in soil for contact with, and as a water and nutrient source for, plants roots, but have not been recognized to provide sufficient free swell when in contact with salt water for purposes of waterproofing salt water-contacting surfaces, as described in U.S. patent application Ser. No. 11/469,273 and U.S. Pat. No. 5,317,834.
This assignee also has a number of patents directed to fresh water-swellable compositions comprising a nonhydrated bentonite clay that is intimately contacted with a tackifying or plasticizing agent such as polybutene, polypropene, polybutadiene, polyisobutene and/or polyisopropene, or mixtures and admixed with an elastomer, such as butyl rubber, that is capable of fresh water swell and capable of stretching or expanding when hydrated with fresh water. See, for example U.S. Pat. Nos. 4,656,062; 4,810,573; 4,773,989; 4,787,780; 4,668,724; 4,534,926; and 5,580,630.